US2018055427A1PendingUtilityA1
Method and Apparatus to Enhance Peripheral Venous Oxygen Measurements
Est. expiryAug 24, 2036(~10.1 yrs left)· nominal 20-yr term from priority
A61B 5/1495A61B 5/14551A61B 5/1491A61B 5/6826A61B 5/0053A61B 5/0051A61B 5/7257A61B 5/6806A61B 5/01
35
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
A method and apparatus for non-invasive measure of venous oxygen saturation, which can be useful for early diagnosis of microcirculatory dysfunction and treatment of medical conditions, such as septic shock, is disclosed. The method applies external stimulus to a patient to improve the signals to an oximeter yielding more reliable measurements. The device implementing the method uses superficial low frequency and low pressure pulse to the patient near the site of the oximeter as well as optionally controlling the patient's temperature near the site of the oximeter. The results also include non-invasive measurements of SpaO 2 , SpvO 2 and O 2E .
Claims
exact text as granted — not AI-modifiedWhat is claimed:
1 . A method for non-invasively measuring venous oxygen saturation of a subject, comprising:
applying a pressure transducer at a first site on a subject having venous and arterial systems; applying a drive signal to the pressure transducer at a frequency below about 0.83 Hz to cause a series of pulsations of a magnitude in the venous blood volume less than diastolic pressure of the subject such that the arterial system is minimally disturbed; applying an oximeter device at a second site on the subject; measuring output signals received from the oximeter device, the output signals containing a component representative of the modulation of venous blood volume due to the series of pulsations; and deriving a measure of venous oxygen saturation of the subject from the frequency response of the output signals.
2 . The method of claim 1 , further comprising controlling the temperature of the subject at the second site.
3 . The method of claim 2 , wherein the temperature is above about 30° C.
4 . The method of claim 2 , wherein the temperature is within a range of from about 30° C. to about 35° C.
5 . The method of claim 1 , wherein the frequency is within a range of from about 0.1 Hz to about 0.83 Hz.
6 . The method of claim 1 , wherein the frequency is about 0.2 Hz.
7 . The method of claim 1 , wherein the magnitude of the series of pulsations is a pressure within a range of from about 10 mmHg to about 80 mmHg.
8 . The method of claim 1 , wherein the magnitude of the series of pulsations is a pressure of about 40 mmHg.
9 . The method of claim 1 , wherein the measure of venous oxygen saturation is derived from the following equations:
R
Ven
=
(
APG
H
z
/
D
C
0
H
z
)
RD
(
APG
H
z
/
D
C
0
H
z
)
IR
,
wherein
R Ven is the modulation ratio related to venous blood,
|APG| Hz is the peak Fourier magnitude at the applied pulse frequency of the APG signal,
|DC| 0 Hz is the peak Fourier magnitude at 0 Hz frequency of the DC signal; and
SpvO 2 =110−40* R Ven
wherein SpvO 2 is the pulse oximeter estimation of SvO 2 .
10 . The method of claim 1 , further comprising deactivating the pressure transducer and determining the arterial oxygen saturation.
11 . The method of claim 10 , wherein the determination of arterial and venous oxygen saturation use different calibration equations.
12 . An apparatus for non-invasively measuring venous oxygen saturation of a subject, comprising:
a pressure transducer capable of applying a series of pulsations to a first site on a subject having venous and arterial systems; a pulse oximeter; optionally a heat source; optionally a temperature sensor; a controller in communication with the pressure transducer, pulse oximeter, optional temperature sensor and optional heat source, wherein the controller is capable of applying a drive signal to the pressure transducer at a frequency below about 0.83 Hz to cause a series of pulsations of a magnitude in the venous blood volume less than diastolic pressure such that the arterial system is minimally disturbed, optionally controlling the temperature of the subject at a second site, and measuring output signals from the pulse oximeter, the output signals containing a component representative of the modulation of venous blood volume due to the series of pulsations; and a signal processor capable of extracting a value for venous oxygen saturation from the frequency response of the output signals.
13 . The apparatus of claim 12 , wherein the temperature is above about 30° C.
14 . The apparatus of claim 13 , wherein the temperature is within a range of from about 30° C. to about 35° C.
15 . The apparatus of claim 12 , wherein the frequency is within a range of from about 0.1 Hz to about 0.83 Hz.
16 . The apparatus of claim 12 , wherein the magnitude of the series of pulsations is a pressure within a range of from about 10 mmHg to about 80 mmHg.
17 . The apparatus of claim 12 , wherein the signal processor is capable of deriving the venous oxygen saturation from the following equations:
R
Ven
=
(
APG
H
z
/
D
C
0
H
z
)
RD
(
APG
H
z
/
D
C
0
H
z
)
IR
,
wherein
R Ven is the modulation ratio related to venous blood,
APG| Hz is the peak Fourier magnitude at the applied pulse frequency of the APG signal,
|DC| 0 Hz is the peak Fourier magnitude at 0 Hz frequency of the DC signal; and
SpvO 2 =110 −40* R Ven
wherein SpvO 2 is the pulse oximeter estimation of SvO 2 .
18 . The apparatus of claim 12 , wherein the frequency is about 0.2 Hz.
19 . The apparatus of claim 12 , wherein the magnitude of the series of pulsations is a pressure of about 40 mmHg.Cited by (0)
No later patents cite this yet.
References (0)
No backward citations on record.